Rats made hypothyroid by surgical thyroidectomy were· compared with controls relative to the shortening velocity and maximum shortening ability of the intestinal smooth muscle and the gastrocnemius. Hypothyroidism showed some potentiation of maximum shortening, but no effect on the shortening velocity of the gastrocnemius. Intestinal smooth muscle maximum shortening as well as shortening veloci...

Aging is the accumulation of changes in an organism over time that leads to reduced viability. Studies in model organisms indicate that aging is genetically determined and that alterations to specific genes can extend or shorten lifespan. Some organisms exhibit negligible aging with no loss of metabolic functions or fertility over time, despite a high metabolic rate, raising the question as to ...

We examined the tension change induced by a rapid temperature jump (T-jump) in shortening and lengthening active muscle fibres. Experiments were done on segments of permeabilized single fibres (length (L0) approximately 2 mm, sarcomere length 2.5 microm) from rabbit psoas muscle; [MgATP] was 4.6 mm, pH 7.1, ionic strength 200 mm and temperature approximately 9 degrees C. A fibre was maximally C...

The extra heat liberation accompanying muscular shortening, the force-determined shortening heat, is defined as the difference between the heat produced when shortening occurs and that produced in an isometric contraction developing the same amount of force and performing the same amount of internal work. Based on this definition, the initial energy production in twitches and tetanic contractio...